The Boston Claude D. Pepper Older Americans Independence Center (OAIC) is a multi-institutional research network focused on fostering translational research in function promoting therapies that reduce the burden of disabling functional limitations in older adults. This application requests supplemental funding to the OAIC?s Pilot and Exploratory Studies Core (PESC). It will enable a pilot study of the effects of transcranial direct current stimulation (tDCS)?a noninvasive means of modulating neuronal excitability within the brain?on cognition and mobility in older adults with mild Alzheimer?s disease (AD). This study builds upon work by Drs. Brad Manor (PESC Awardee), Lewis Lipsitz (OAIC REC Director), and Thomas Travison (OAIC BDAC Director) at Hebrew SeniorLife?s Institute for Aging Research showing that tDCS targeting the left dorsolateral prefrontal cortex (dlPFC) improved cognition, as well as the ability to stand and walk while performing cognitive tasks (i.e., dual tasking) in older adults with executive dysfunction and slow gait. Our scientific premise is that AD neuropathology, even in its early stages, affects the prefrontal lobes and leads to executive dysfunction, dual tasking deficits and mobility disturbances. As such, tDCS that facilitates the excitability of the prefrontal cortex and its connected neural networks holds promise to combat the early cognitive and mobility impairments of AD, and ultimately lead to more functional independence and fewer falls. Our Specific Aim is to conduct a pilot, randomized controlled trial to determine the feasibility and effects of a 10-session personalized tDCS intervention targeting the left dlPFC on cognitive function, dual task standing and walking, and other metrics of mobility in 24 older adults with mild AD living in supportive housing. To date, tDCS interventions have attempted to optimize current flow to the target region via modeling of a ?typical? brain and have thus not accounted for individual differences in skin, skull, cerebrospinal fluid and brain tissue in the aging brain. We propose to overcome this limitation by implementing an innovative optimization procedure, called Stimweaver, that uses individual structural brain MRIs to model current flow and determine electrode placement and flow parameters that optimize flow to the left dlPFC of each participant. This project is thus innovative, highly compatible with the Boston OAIC theme, and will enable the team to develop a new focus on AD. It will stimulate future research activity by establishing optimal methods for recruitment and retention, estimates of inter-subject variance in study outcomes, and the effects of personalized tDCS in this population.